MAC-level measurement based traffic distribution over IEEE 802.11 multi-radio networks

It is expected that multiple radio access technologies coexist within a single terminal. In those networks, we focus on the problem of how to distribute IP traffic into multiple underlying links in order to enhance the overall aggregated throughput. As an effective aggregation mechanism, traffic is equivalently assigned to each link, in proportion to its available capacity. To this end, the capacity of each link is commonly measured for easy comparison between radio links, and then, the relative split ratio is accordingly determined. We identify LTT (link transmission time) as a common link resource measure. We specifically consider that each terminal is equipped with IEEE 802.11a and 802.11b devices, and have implemented a practical testbed network system. In IEEE 802.11 networks, LTT is considerably variable due to random back-off process, depending on neighboring contending terminals and radio signal quality variations. It is actually captured at a radio device driver instead of theoretical calculation. Based on measurements, we determine traffic split ratios to both links. Extensive experimental results show that the proposed method could reduce the packet reorder delay at the receiver by achieving equal load-balance, rapidly adapting to varying link qualities (i.e., channel access contention and radio signal attenuation).